In order to minimize the evaporative loss of fuel to the atmosphere from motor vehicle gasoline tanks, a vent line is typically attached to the tank for directing fuel vapors to storage containers such as charcoal cannisters and/or to the engine such as to the fuel-air intake manifold. Such vent lines may be susceptible to fuel leakage from the fuel tank in the event of an accidental roll-over of the automobile or even when the automobile is tilted to an extreme angle such as may occur if a motor vehicle runs off the road over an embankment or into a ditch. Fuel leakage from the fuel tank vent line is to be avoided if possible. Thus, it has become common to include a positionally sensitive roll-over valve in the vent line to close it when the automobile has been titled in excess of a predetermined angle or has rolled over and is upside down. The closed valve prevents leakage of fuel from the tank through the vent lines and thus minimizes the possibility of a fire hazzard which may result therefrom.
An object of this invention is to provide an improved roll-over valve which reacts positively both to open itself and to close itself when its position is changed.